Massachusetts Institute of TechnologyLaboratory for Electromagnetic and Electronic Systems

Group Meeting July 21, 2009

Justin Burkhart

Presentation Outline

More Exact Analysis of Class E Resonant Boost Converter

Gate Drive Options

Transistor Layout Optimization

Boost Converter Operation

Switch is opened and closed periodically The rectifier LC tank is assumed to have high Q such

that the current in L2 is purely sinusoidal

L1 and C1 are tuned such that when the switch is opened, the voltage across the switch will ring back to zero half of a period later

Delivery of Power

Inverter(lossless)

Rectifier(lossless)+

-+-

Vin Vout

Pin Pinv Pout

Pin = Pinv = Pout

Delivery of Power

Inverter(lossless)

Rectifier(lossless)+

-+-

Iin-dc+I1sin(wt)+I2sin(2wt)+…

Vin Vout

Pin Pinv Pout

Pin = Pinv = Pout

Pin=VinIin-dc

Delivery of Power

Inverter(lossless)

Rectifier(lossless)+

-+-

Iin-dc+I1sin(wt)+I2sin(2wt)+… Iout-dc+Io1sin(wt)+Io2sin(2wt)+…

Vin Vout

Pin Pinv Pout

Pin = Pinv = Pout

Pin=VinIin-dc Pout=VoutIout-dc

Delivery of Power

Inverter(lossless)

Rectifier(lossless)+

-+-

Iin-dc+I1sin(wt)+I2sin(2wt)+… Iinv-dc+I1-invsin(wt)

Vin Vout

Pin Pinv Pout

Pin = Pinv = Pout

Pin=VinIin-dc Pout=VoutIout-dcPinv=PAC+PDC

Iout-dc+Io1sin(wt)+Io2sin(2wt)+…

Inverter: Detailed Analysis

Unknowns: wo, zo, IAC, o1, IL(0)

Constraints: <IL(t)> = Pout/Vin, <VC(t)> = VIN, <VC’(Ts/2)> = 0, 0.5 VC-Fund IAC cos(o-o1) = Pout(1-Vin/Vout)

Known Initial Conditions: Vc(0)=0

wo,zo

0 10 20 30 40 50-0.5

0

0.5

1

1.5

Time (ns)

Cur

rent

(A) io(t)

I

0 10 20 30 40 50

0

20

40

Time (ns)

Vol

tage

(Vol

ts) V(t)

Vo(t)

Inverter: Detailed Analysis

Unknowns: wo, zo, IAC, o1, IL(0)

Constraints: <IL(t)> = Pout/Vin, <VC(t)> = VIN, <VC’(Ts/2)> = 0, 0.5 VC-Fund IAC cos(o-o1) = Pout(1-Vin/Vout)

Known Initial Conditions: Vc(0)=0

0 10 20 30 40 50-0.5

0

0.5

1

1.5

Time (ns)

Cur

rent

(A) io(t)

I

0 10 20 30 40 50

0

20

40

Time (ns)

Vol

tage

(Vol

ts) V(t)

Vo(t)

Solve system of non-linear equations for each value of wo

wo,zo

Rectifier: Detailed Analysis

0 10 20 30 40-20

0

20

40

Time (ns)

Vol

tage

(Vol

ts)

VAC+VDC

0 10 20 30 40-50

0

50

Time (ns)

Vol

tage

(Vol

ts)

Vdiode(t)

0 10 20 30 40-2

0

2

4

Time (ns)

Cur

rent

(Am

ps)

Io(t)

Unknowns: wr, zr, ton, toff

Constraints: <VD(t)> = VIN, <IL(t)> = POUT/VOUT, IAC and o1 are constrained by the inverter

Known Initial Conditions: VD(toff) = VOUT, IL(toff) = 0

Rectifier: Detailed Analysis

0 10 20 30 40-20

0

20

40

Time (ns)

Vol

tage

(Vol

ts)

VAC+VDC

0 10 20 30 40-50

0

50

Time (ns)

Vol

tage

(Vol

ts)

Vdiode(t)

0 10 20 30 40-2

0

2

4

Time (ns)

Cur

rent

(Am

ps)

Io(t)

Unknowns: wr, zr, ton, toff

Constraints: <VD(t)> = VIN, <IL(t)> = POUT/VOUT, IAC and o1 are constrained by the inverter

Known Initial Conditions: VD(toff) = VOUT, IL(toff) = 0Solve system of non-linear equations

Gate Drive Options

Hard Switched Gate DriveLoss arises from charging and discharging CISS

through a resistor every cycle. Thus, loss is proportional to switching frequency. Since the converter is operating at 75 MHz this loss can be substantial, however, this scheme has very low complexity.

Resonant Gate DriveAn inductor can be added in series with the gate to form a resonant circuit with CISS. This essentially charges and discharges CISS with a sinusoidal current. Loss occurs in RISS.

Introduction to TI’s LBC5 Process

Removed

LDMOS Layout

Removed

LDMOS Layout Optimization

Large LDMOS transistors are formed by connecting many smaller transistors in parallel

Optimization serves to find the total device size, finger size, finger layout, and metal layout that achieves the highest converter efficiency

Loss Model:

Scaling of Parasitics

Removed

Optimization Procedure

Sweep total device width Sweep number of fingers

Calculate loss

Choose total device width and number of fingers

Find best aspect ratio and top metal layer layout

Solid Lines: Ross set by scaling measured dataDashed Lines: Ross set as 3 Rds

Optimization Result (Hard Switched)

Optimization Result (Hard Switched)Solid Lines: Ross set by scaling measured dataDashed Lines: Ross set as 3 Rds

Choose 45000um and 100 Fingers

Optimization Result (Resonant Gating)Solid Lines: Hard SwitchedDashed Lines: Resonant Gating

Choose Aspect Ratio

Total Area Available: 1500x1000 um Finger Cross Section: 13.8 um Finger Width: 245 um

# of Rows Total Length (um) Total Width (um)

1 1380 245

2 690 490

3 460 735

4 345 980

Choose Aspect Ratio

Total Area Available: 1500x1000 um Finger Cross Section: 13.8 um Finger Width: 245 um

# of Rows Total Length (um) Total Width (um)

1 1380 245

2 690 490

3 460 735

4 345 9803 rows is chosen

Top Metal Design

Top Metal Design Metal 1

Gate

Top Metal Design Metal 1 Metal 2

Sour

ce

Top Metal Design Metal 1D

rain

Metal 2

Top Metal Design Metal 1 Metal 2

Sour

ce

Dra

in

Taper Angle Optimization

Adjust the size of the network based on the number of fingers per row and solve for equivalent resistance using MATLAB

NodeMatrix

VoltageVector

ConstantVector

Taper Angle Optimization

0 10 20 30 40 50 60300

350

400

450

500

550

600

650

700

750

800

Taper Angle (degree)

On

Res

ista

nce

(mO

hm)

On-State Resistance vs. Geometry

100 Fingers/Row50 Fingers/Row33 Fingers/Row25 Fingers/Rows10 Fingers/RowMinimum Possible

Optimization ignores metal resistance in connecting rows

Device Layout

Ideas for Improvement?Break long rows into multiple columns

Ideas for Improvement?

Gate

Metal 1 Metal 2

Ideas for Improvement? Metal 1 Metal 2

Ideas for Improvement? Metal 1 Metal 2

Source